Watch the Oroville Dam spillway reopen

In a new test of Oroville Dam’s battered infrastructure, water resumed flowing down the fractured main spillway Friday, March 17, 2017, after a three-week shutdown, as state officials concentrate on reducing water levels at the troubled reservoir.

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In a new test of Oroville Dam’s battered infrastructure, water resumed flowing down the fractured main spillway Friday, March 17, 2017, after a three-week shutdown, as state officials concentrate on reducing water levels at the troubled reservoir.

What went wrong at Oroville? Congressional Democrats demand answers

Citing the near disaster at Oroville Dam, a group of congressional Democrats is pushing the government’s watchdog agency to investigate federal oversight of dam safety regulations.

The group, including Rep. Doris Matsui of Sacramento and five other Californians, called on the Government Accountability Office to look into the Federal Energy Regulatory Commission’s handling of the licensing of major dams.

The February crisis at Oroville “raises questions about deficiencies in FERC’s safety program and concerns over the potential for severe property damage, injury and even possible loss of life,” the group said in a letter released Wednesday.

Separately, the California state Senate Natural Resources and Water Committee will hold an oversight hearing on Oroville next Tuesday. The hearing comes as elected officials push the state Department of Water Resources to release more information about the Oroville investigation and repairs. DWR has sealed several key documents, citing security concerns.

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The congressional Democrats are focused mainly on FERC’s decision to brush aside calls, made by a coalition of environmentalists from 2003 to 2005, for an order requiring the California Department of Water Resources to line Oroville’s emergency spillway with concrete. Although DWR runs the dam, FERC licenses it because of its hydroelectric plant.

FERC decided the emergency spillway was safe. DWR also dismissed the warnings, as did the local water agencies that take water stored in Lake Oroville. The local agencies, including organizations such as the Metropolitan Water District of Southern California, would have had to pay for the upgrade.

The crisis at Oroville began when the dam’s main spillway cracked in two Feb. 7, prompting dam officials to halt water releases temporarily despite a heavy rainstorm. The reservoir filled so high that water flowed over the adjacent emergency spillway, which consists of a concrete lip perched atop the unlined hillside, for the first time ever. One day later, the hillside was eroding so badly that officials feared the emergency spillway would fail. They ordered the evacuation of 188,000 downstream residents.

“The Oroville Dam failure did not come without warning,” the congressional Democrats wrote in their letter to the GAO.

Catastrophe was averted when DWR’s dam operators dramatically increased water releases from the damaged main spillway, which brought lake levels down and halted the flows over the emergency structure. Since then, work crews have been fortifying the upper hillside with rocks and concrete. DWR has said it plans to line at least part of the hillside with concrete as part of a two-year, $275 million permanent repair plan for the two spillways.